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Thursday, Aug. 25, 2016

Local Soybean Rust is National News

Tuesday, October 23, 2007

During the past two summers, Owen and Clay County Extension staff has been working to monitor and sample both a soybean field and a kudzu patch to monitor for the relatively new Asian Soybean Rust (SBR).

For the first time, leaves collected this past Monday were found positive for the SBR fungus in Owen County. A double crop soybean field near the Owen-Putnam County line had two of 100 leaves where the fungus was found.

One leaflet had several pustules scattered over the surface, and these were all producing spores. A second leaf had two lesions that appeared to be SBR pustules that had not yet reached the stage of spore production. This SBR poses absolutely no threat to our soybean crop. Finding SBR now does not mean our risk of SBR is any greater for next year.

Once there is a killing frost, any SBR in Indiana will be eliminated. However, this finding has huge research and modeling significance. The local Extension staff would like to thank the Cloverdale Agri-Center and the Indiana Department of Natural Resources for assisting with soybean and kudzu, respectively, sample sites.

Blown into the United States during the bad hurricane summer when Katrina and other storms struck the Gulf Coast, SBR became a real concern at that time.

No one knew how quickly it would spread in future years but it was known that most likely SBR would only overwinter in the warm confines of the Gulf Coast area where hard freezes do not occur and hosts like kudzu and volunteer soybean are available year around. Thankfully the fungus has stayed in the Gulf Coast states for the most part and has not been an economic issue here locally during the growing season. However as the SBR fungus gets a stronger bank of spores developed in the Gulf Coast area over time, it is believed that with the right weather conditions and southwesterly flow of summer winds that locally SBR will be an economic threat during the growing season sometime in the future.

The main importance of the Owen County finding is for the people who are modeling the continental spread of SBR spores by wind and deposition of spores by rain. This will provide another data point, which can be compared with predicted dispersal over the past 3 weeks. Also for local farmers and agricultural vendors, this finding really illustrates the value of sentinel plots and the importance of staff taking time to scout and sample fields.

If we had to rely on casual observations to detect SBR, this would never have been found. By the systematic sampling of leaves throughout the season, even these leaves represent a very small fraction of all soybean leaves in the state, we have a much better chance of finding these rare infections.

Ultimately SBR will become a reality during the growing season locally when spore banks are sufficiently built in the non-freezing areas of the Gulf Coast states. We feel confident that low levels of SBR will be detected quickly such that treatments can be made. The SBR fungus can quickly advance within a field, as a soybean field can appear healthy one day and six days later be brown and defoliated.

The warm weather, heavy dew and recent showers have accelerated growth of lost corn and soybean grain during the harvesting process.

Much of the soybean loss was unavoidable as grain was very dry, with green plants slowing harvest speed. Pod shatter likely accounted for much of the loss. Now that the double crop soybeans have lost their leaves, we will start monitoring the volunteer soybeans coming up in a neighboring field where the SBR was found until there is a freeze.

There has long been debate about whether SBR develops on beans before R1"sampling volunteer beans in an area where SBR is known to be present would be a good test of who is correct. Visit http://www.ppdl.purdue.edu/PPDL/SBR/07AS... to see more about SBR and to follow the advance of SBR.

You can contact the local Purdue Extension Office by calling 829-5020 x14 in Owen County or 448-9041 in Clay County for more information or publication copies regarding this week’s column topic or to RSVP for upcoming events.

It is always best to call first to assure items are ready when you arrive and to RSVP for programs. While most publications are free, some do have a fee. All times listed are Eastern Time.

Upcoming Events

Nov. 1-2 Mineral Education Workshop for Teachers, Terre Haute/ Farmersburg

Nov. 3 Owen Extension Annual Meeting w/ Tom Turpin, 6:30 p.m.